1. Technical Field
This invention generally relates to underground boring equipment. More particularly, the invention relates to a cutting head for use with an auger boring machine to bore through a body of soil and simultaneously lay an underground pipe. Specifically, the invention relates to a collapsible rock head which cuts rock forward of the underground pipe when expanded and which may be collapsed so that it can pass through the pipe.
2. Background Information
The use of auger boring machines to lay underground pipe without causing damage to surface structures such as roadways is well known. In this procedure, the boring machine is used to form a generally horizontal hole or passageway through the soil at an appropriate depth. The boring machine may be positioned adjacent a hillside for boring into the hillside or an excavation pit may be dug in the ground to accommodate the boring machine at the appropriate boring depth. The boring machine is typically mounted on tracks so that it is able to slide toward and away from the surface into which the hole is being bored. Once the boring machine is in position, a flighted auger is operationally connected to the boring machine and an appropriate cutting head is attached to the front of the auger. The cutting head is placed into contact with the soil face and the auger and cutting head are rotated by the boring machine so that the cutting head bores into the soil while the helical auger flights direct excavated material away from the cutting head and out of the hole. Additional sections of auger are added as needed by sliding the boring machine away from the hole, positioning a new auger section rearwardly of the first auger section typically using a crane, and then securing the auger sections together. The boring machine is advanced forward along the tracks toward the soil face until the next auger section is needed, and then another auger section is attached thereto. This procedure is repeated until the desired length of hole is cut through the soil.
When laying the pipe at the same time as excavating the hole or passageway, each section of auger is inserted into a section of casing or pipe before it is lowered into place in front of the boring machine. The boring machine then advances both the pipe and auger as the cutting head cuts through the soil. The machine pushes the pipe through the soil substantially without rotation while rotating the auger within the pipe. Subsequent sections of auger and pipe are connected as needed. The sections of auger are connected together typically using male and female hex connectors. The sections of pipe are secured together by welding.
The cutting head selected for boring operations is dependent upon the type of substrate that is being drilled. If the substrate is generally soil with small stones interspersed therethrough, then the type of cutting head used is known as a dirt head. Dirt heads cut easily and efficiently through soil. During boring operations, the dirt head sometimes strikes a large rock or a layer of rock. Dirt heads are ill equipped to cut through rock. Rock heads are specially designed to cut through rock, but are far less efficient at cutting through soil.
It used to be a very time consuming process to replace the dirt head with a rock head to cut through the rock, as detailed in U.S. Pat. No. 7,367,421 granted to Barbera et al. Said patent describes a collapsible rock head used in overcoming such time consuming processes. Generally, Barbera et al. describes the method of cutting appropriate substrate with a dirt head until it encounters a large rock or rock layer, at which time the dirt head and auger are withdrawn through the underground pipe so that the dirt head may be replaced with a collapsible rock head. The rock head and auger are then be inserted and advanced through the pipe such that the rock head automatically expands pivotally mounted rock cutters via spring bias to an expanded position forward of the pipe in order to cut through the rock a hole of sufficient diameter to allow the pipe to be inserted therethrough.
Although collapsible rock heads are known generally, there is still a need in the art for improved collapsible rock heads, such as provided by the present invention.